The present invention relates to electronic circuits, and in particular, to circuits and methods for automatic power source detection.
Electronic systems require a source of power to operate. Typically, an electronic system has a connection to an external power source, such as power delivered from a power outlet in a wall plug, for example, through a power cable. External power may be used to power the electronic system and/or charge a battery in the electronic system, for example. FIG. 1 shows a typical configuration for delivering power to an electronic system and/or to charge a battery in the system. An external power source is coupled to an electronic system 103 through a power adapter 101 and regulator 102. For example, the power source may be a wall plug and power adapter 101 may be a wall adapter having a plug and circuitry for receiving an alternating current (“AC”) voltage and current and outputting a direct current (“DC”) voltage and current. As another example, power adapter 101 may be a personal computer coupled to the power source through a power cord. A personal computer or other electronic device may also have an internal battery that acts as the power source, for example, to another electronic device 103. A personal computer may output DC voltage and current on a port, such as a Universal Serial Bus (“USB”) port, for example, which may be used to provide power to system 103 through regulator 102.
One problem with receiving power in an electronic system pertains to the specifications of voltage and current received at the input of the electronic system. Different power adapters may have drastically different voltage and current output specifications and capabilities. For example, some wall adapters may output 5 volts and a maximum of 1500 mA or higher voltages and currents. Other power adapters, such as a USB power source, may provide 5 volts and a maximum current output of 100 mA or 500 mA. Yet other wall adapters may output 12 volts and a maximum current output of 2000 mA.
Embodiments of the present invention include circuits and methods for use in an electronic system for receiving and using power from a wide variety of power adapters.